Lightweight Valve

ABSTRACT

A lightweight valve ( 1 ), in particular for internal combustion engines, is provided, with a valve stem ( 3 ), with a hollow valve cone ( 5 ) and with a valve disk ( 7 ) closing the valve cone ( 5 ), the valve disk ( 7 ) being provided with a recess ( 23 ) on its flat side facing the valve cone ( 5 ). The lightweight valve ( 1 ) has a valve cone ( 5 ) projecting with its end region of greater diameter into the recess ( 23 ).

The invention relates to a lightweight valve, in particular for internalcombustion engines, according to the preamble of claim 1.

Lightweight valves of the kind referred to here are known (DE 198 04 053A1). They are used inter alia as inlet and outlet valves for internalcombustion engines and comprise a solid or hollow valve stem having onlya small wall thickness, a funnel/trumpet-shaped valve cone and a valvedisk for closing the valve cone, the valve disk being, for the purposeof weight reduction, provided with a recess on its flat side facing thevalve cone. The recess is spaced from the peripheral surface of thevalve disk, so that a plane annular surface, on which the valve cone isbrought to bear with the face of its end of greater diameter, is formedat the edge. Valve cone and valve disk are welded together in theirconnection region. It is a disadvantage of the known lightweight valvethat accurate, relative alignment of the individual parts, in particularof the valve cone in relation to the valve disk, can be brought aboutbefore the joining process only with great effort and special holdingdevices are necessary, which hold the valve cone and the valve disktogether positionally accurately during the joining process.

It is an object of the invention to provide a lightweight valve of thekind referred to in the introduction which does not have thisdisadvantage.

To achieve the object, a lightweight valve with the features of claim 1is proposed. This is characterized in that the valve cone projects withits end region of greater diameter into the recess. By virtue of thisdesign, accurate alignment of valve cone and valve disk in relation toone another is brought about in a simple way without special devicesbeing necessary for this. Furthermore, the engagement of the valve conein the recess secures the valve disk against radial displacementrelative to the valve cone. It is moreover advantageous that the designaccording to the invention of the connection region affords more weldseam formation possibilities than the known lightweight valve.

According to a first embodiment, the valve cone and the valve stem aredesigned as a one-piece component. In this connection, the valve conecan be produced on the valve stem by flaring, that is by expanding thehollow stem end. According to a second embodiment of the lightweightvalve, the valve cone is a separate component which is fixed at its endof smaller diameter to the valve stem or to a stem connection elementprovided on the valve disk and extending through the valve cone and atits end of greater diameter to the valve disk.

The diameter of the recess and the outside diameter of the valve cone atits end of greater diameter can be matched to one another in such a waythat, when the valve cone is introduced into the recess, a non-positiveconnection is formed between these parts, by virtue of which these areinterconnected non-displaceably and captively. This simplifies thehandling of this subassembly formed by insertion of the valve cone intothe valve disk recess during the subsequent joining process, that iswhen valve cone and valve disk are materially interconnected, preferablywelded or soldered together. Further fastening means for connecting thevalve disk and the valve stem for the purpose of pre-assembly are notnecessary.

In an especially advantageous illustrative embodiment of the lightweightvalve, the recess in the valve disk is designed as a centering and/orsupporting seat. In this connection, the recess is preferably designedin such a way that a desired alignment of the valve cone relative to thevalve disk takes place during introduction of the end region of greaterdiameter of the valve cone, so that it is possible to dispense withseparate centering means. In this connection, the recess servesadditionally or alternatively as a bearing for the valve cone.

In an advantageous illustrative embodiment, the valve disk is made fromthe intermetallic phase titanium aluminide (TiAl) or a TiAl alloy bycasting. This valve disk has only low weight and is moreover extremelywear-resistant. According to another variant embodiment, the valve diskis made of steel, in particular tool steel, and is produced by forging.According to a third variant embodiment, the valve disk is manufacturedby means of a powder metallurgy production process, in particular from atool steel which is extremely wear-resistant.

As far as the materials which can be used for the valve stem and thevalve disk are concerned, reference is made to DE 100 29 299 C2, thecontent of which with regard to the materials used is a subject of thisdescription.

In an especially preferred illustrative embodiment of the lightweightvalve, the valve cone is designed as a sheet metal component.High-carbon structural steel, in particular St-52, or low-alloy steel,in particular X10Cr13, for example, is used as the material. The valvecone can be produced cost-effectively by deep-drawing.

Further advantageous illustrative embodiments of the lightweight valveemerge from combinations of the features referred to in the descriptionand in the subclaims.

The invention is explained in greater detail below with reference to thedrawings, in which

FIG. 1 shows a detail of a first illustrative embodiment of alightweight valve for internal combustion engines in a perspective,cutaway illustration;

FIG. 2 shows a perspective illustration of a valve cone illustrated inFIG. 1;

FIG. 3 shows a perspective, cutaway illustration of a detail of afurther illustrative embodiment of a valve disk;

FIG. 4 shows a detail of a third illustrative embodiment of thelightweight valve in a perspective, cutaway illustration, and

FIG. 5 shows a detail of a fourth illustrative embodiment of thelightweight valve in a sectional illustration.

FIG. 1 shows part of a first illustrative embodiment of a lightweightvalve 1 of multi-part design for internal combustion engines. This canbe used as a thermally less loaded inlet valve or as a thermally morehighly loaded outlet valve, the material of the individual parts beingselected accordingly depending on the use of the lightweight valve 1.

The lightweight valve 1, which is rotationally symmetrical about itslongitudinal central axis 2, comprises a valve stem 3, made of solidmaterial here, a hollow valve cone 5 and a valve disk 7 closing thevalve cone 5.

The valve stem 3, which has a circular cross section, has a longitudinalportion 9 of greater diameter which is adjoined by a longitudinalportion 11 of smaller diameter, by virtue of which an all-round annularbearing shoulder 15 is formed on the outer peripheral surface 13 of thevalve stem. Alternatively, for reasons of weight reduction, the valvestem 3 can also have a hollow space. The valve stem 3 can, for example,be formed by a precision-drawn tube made of steel, for example X45,which is closed at the end which is not illustrated by means of a valvestem endpiece/foot. The valve stem 3 has a plane end face 17 at its endwhich can be seen in FIG. 1.

The valve cone 5 illustrated in FIGS. 1 and 2 is formed by a separatesheet-metal part and has only a small wall thickness. The one-piecevalve cone 5 has a basic body in the shape of a disk spring, on the endof smaller diameter of which a collar-shaped guiding and centeringportion 19 is formed, which is perforated by a through-opening 21,through which the valve stem 3 extends in the joined-together state. Thediameter of the through-opening 21 is the same as or greater than theoutside diameter of the valve stem 3, so that either the latter extendsthrough the through-opening 21 with play or a non-positive connection isformed between valve stem 3 and valve cone 5. When the valve cone 5 ispushed onto the valve stem 3, these parts are automaticallyaligned/centered in relation to one another owing to the guiding andcentering portion 19.

The valve disk 7 is provided on its flat side facing the valve stem 3with a recess 23 which serves as a bearing/seat for the valve cone 5 andinto which the valve cone 5 projects with its end of greater diameter.Seen in top view, the recess 23 has a circular cross section. In thisconnection, the recess 23 is designed in such a way that the transitionbetween valve disk 7 and valve cone 5 in their connection region iscontinuous. The hollow space of the valve cone 5 is closed by means ofthe valve disk 7. In the illustrative embodiment shown in FIG. 1, thebottom of the recess 23 is of plane design. The side wall 25 of therecess 23 extends perpendicularly to the bottom of the recess 23. Thediameter of the recess 23 and the outside diameter of the valve cone 5at its end of greater diameter are the same or approximately the same.

As can be seen from FIG. 1, the end face 27 of greater diameter of thevalve cone 5 is located opposite the recess side wall 25, that is it isarranged completely in the recess 23. The valve cone 5 is introducedinto the recess 23 with its end of greater diameter until it comes upagainst the bottom of the recess 23. A reproducible arrangement of thevalve cone 5 in relation to the valve disk 7 is therefore brought aboutin a simple way.

The valve disk 7 is of disk-shaped design and has a first, cylindricallongitudinal portion 29 of constant cross section and, adjoining this, aconical second longitudinal portion 31A and also, adjoining this, aconical third longitudinal portion 31B, the cone angle of the thirdlongitudinal portion 31B being the same as the cone angle of the valvecone 5 at its end of greater diameter, by virtue of which a continuoustransition is brought about in the connection region between theseparts.

In the properly joined-together state, the end face 17 of the valve stem3 bears flat against the bottom of the recess 23, as illustrated inFIG. 1. The valve disk 7 is therefore supported by the valve stem 3 onits flat side facing away from the combustion chamber, so that optimumintroduction of the gas forces acting on the valve disk 7 into the valvestem 3 can be ensured, without inadmissibly great deformations of thevalve disk 7 and of the valve cone 5 arising in this connection. Owingto the design according to the invention of the lightweight valve 1, itis possible to ensure that the valve cone 5 is virtually force-freeduring operation of the lightweight valve 1, that is that only verysmall forces—if any—are introduced into the valve cone 5 via the valvedisk 7. The valve cone 5 can therefore be designed with very thin walls,which is advantageous in manufacture of the same and moreovercontributes to reducing the weight of the lightweight valve.

The valve disk 7 and the valve stem 3 are interconnected inseparably bymeans of a material connection. This can be effected by means of, forexample, friction welding, beam welding, fusion welding or capacitordischarge welding. Additionally or alternatively, the valve stem 3 canbe welded together with the valve disk 7 on its end face 17.

Before or after the material connection of valve stem 3 and valve disk7, the valve cone 5 is pushed onto the valve stem 3, in particular untilits end region of greater diameter engages in the recess 23. The valvecone 5 is welded together with the valve stem 3 in the region of theguiding and centering portion 9 and with the valve disk 7 in theconnection region lying in the region of the recess 23, in particularpreferably by means of a friction, beam or fusion welding procedure.

It remains to state that the valve cone 5 has a reduced wall thicknessin the region of its guiding and centering portion 9, so that only anarrow bearing shoulder 15 on the valve stem 3 is sufficient in order tobring about a continuous transition between valve cone and valve stem.

In another illustrative embodiment not shown in the figures, the valvestem 3 has a constant cross section in the connection region of thevalve cone 5, that is on its end region of smaller diameter, by virtueof which an all-round edge step is formed by the end face of the valvecone 5, which step has only a small width, however, owing to the reducedwall thickness of the valve cone 5. The influence on the combustion gasguidance in the region of the outer contour of the valve cone 5 istherefore only slight.

The lightweight valve 1 described above with reference to FIGS. 1 and 2is characterized in particular in that its individual parts can beinterconnected or prefixed in a simple way by fitting together and thatin this connection automatic alignment/centering of the individual partstakes place owing to their constructional design.

The gas forces acting on the valve disk 7 during operation of thelightweight valve 1 are advantageously supported via the valve stem 3bearing centrally against the valve disk 7. In this connection, it canbe ensured that the gas forces acting on the valve disk 7 cannot, or canonly to a harmless extent, be introduced into the very thin-walled valvecone 5. Deformation of the valve cone 5 can therefore reliably beexcluded.

FIG. 3 shows a detail of a second illustrative embodiment of the valvedisk 7. The same parts are provided with the same reference numbers, sothat in this respect reference is made to the description for FIGS. 1and 2. In this illustrative embodiment, three reinforcing ribs 33 moldedinto the valve disk 7 are provided in the recess 23. In the illustrationaccording to FIG. 3, only the reinforcing ribs 33A and 33B can be seen.Seen in a top view of that flat side of the valve disk 7 facing thevalve stem 3, the reinforcing ribs 33 extend radially in relation to thelongitudinal central axis 2 of the lightweight valve 1 and are arrangedat a spacing of 120° from one another. The length of the reinforcingribs 33 originating from the edge region of the recess 23 in thedirection of the valve disk center corresponds approximately to half theradius of the valve disk 7. As can be seen from FIG. 3, the reinforcingribs 33 are in this illustrative embodiment designed as rectilinearstrips of which the height increases in the direction of the valve diskcenter and the width decreases in the direction of the valve diskcenter.

The reinforcing ribs 33 are designed to complement the inner wall of thevalve cone 5, so that the latter, in the joined-together state of thelightweight valve 1, rests flat with its inner wall on the upper narrowside 35 of the reinforcing ribs 33 and is consequently supported bythese. The valve cone 5 and the reinforcing ribs 33 can be welded orsoldered together on their bearing contact region.

As can be seen from FIG. 3, the recess 23 is in its edge region providedwith an all-round edge step 37 which serves for supporting or as abearing shoulder for the valve cone 5 and is designed in such a way thatthe valve cone 5 bears on its inner side against the bottom of the edgestep 37. Such an edge step 37 is also provided in the illustrativeembodiment of the lightweight valve 1 shown in FIG. 1.

The valve disk 7 with the reinforcing ribs 33 designed in one piecethereon can be manufactured cost-effectively by forging owing to itssimple geometry.

It remains to state that the valve stem 3 and the valve disk 7 can bemade from the same material or from different materials. The connectionbetween valve disk 7 and valve stem 3 can in particular be effected bymeans of friction welding, beam welding, fusion welding or capacitordischarge welding in all the illustrative embodiments of the lightweightvalve 1 described with reference to FIGS. 1 to 3 as well. Connecting thevalve disk 7 and the extremely thin-walled valve cone 5 is preferablyeffected by means of beam, fusion or laser welding.

In summary, it remains to state that the lightweight valve 1 accordingto the invention is characterized in particular in that, in addition toits only small weight, it has only a few individual components, whichcan be interconnected with a few simple joining operations, so that itcan be produced cost-effectively overall.

FIG. 4 shows a detail of a further illustrative embodiment of thelightweight valve 1. The same parts are provided with the same referencenumbers, so that in this respect reference is made to the descriptionfor the preceding figures. Here, the valve stem 3 is of tubular designand therefore has a stem hollow space 39, which is closed by means of avalve stem endpiece/foot at the end of the lightweight valve 1 which isnot illustrated. The valve cone 7 is formed by expanding the diameter ofthe valve stem end. The expansion of the valve stem end and the specialshape of the valve cone 5 result in a conical transition from the stemhollow space 39 to the valve cone 7.

A supporting dome 41 which projects beyond the flat side of the valvedisk 7 and has in its center a recess 43 extending in alignment with thestem hollow space 39 is formed on in the center of the valve disk 7. Thesupporting dome 41 has an annular cross section and bears against thevalve cone 5 in the region of its end face 45.

In the illustrative embodiment shown in FIG. 4, the supporting dome 41is connected materially to the valve cone 5 by means of capacitordischarge welding. In this regard, the end face 45 is deformed in such away by partial fusion and pressing of the valve disk against the valvecone that the bearing contact surface 47 of the supporting dome 41 isformed to complement the opposite inner wall region of the valve cone.The valve cone 5 can also be connected to the valve disk 7 at its end ofgreater diameter in the region of the recess 23 by means of capacitordischarge welding, so that fixing can take place in both regionsmentioned in one operation. Other material connection variants are ofcourse also possible.

The bearing contact surface 47 between the supporting dome 41 and thevalve cone 5 can be of all-round design, so that the recess 23 in thevalve disk 7 forms a closed-off annular chamber, the walls of which areformed by the valve disk, the valve cone and the supporting dome. It maybe advantageous to avoid closed-off spaces/chambers, which can bebrought about in the illustrative embodiment shown in FIG. 4 by virtueof, for example, the bearing contact surface 47 being interrupted byslits, so that at least one medium connection exists between therecesses 23 and 43 in the welded state of valve disk 7, or supportingdome 41, and valve cone 5 as well. This makes it possible to excludelocal pressure differences in the lightweight valve 1. The mediumconnection can additionally or alternatively also be formed by one ormore openings/bores extending transversely to the longitudinal extent ofthe supporting dome 41.

The hollow lightweight valve 1, which is closed sealingly at its one endby means of the valve endpiece and at its other end by means of thevalve disk 7, can be filled with a cooling medium, for example sodium.In this connection, both the stem hollow space 39 and the recess 43 inthe supporting dome 41 are filled with the cooling medium, so that bothvalve stem and valve disk and also valve cone are cooled. Provided amedium connection as described above is provided between the recesses 43and 23, the cooling medium also passes into the chamber formed by therecess 23 and can, with an appropriate design of the medium connection,also circulate there, which contributes to improving the heatdissipation from the valve disk.

FIG. 5 shows a detail of a further illustrative embodiment of thelightweight valve 1. Parts which have already been described withreference to the preceding figures are provided with the same referencenumbers, so that in this respect reference is made to FIGS. 1 to 4. Thevalve disk 7 has on its flat side having the recess 23 a stem connectionelement 49 which is designed in one piece with the valve disk 7 and islocated in its center. The stem connection element 49 is at its free endconnected to the valve stem 3, which is effected by means of frictionwelding in the illustrative embodiment shown in FIG. 5. The all-roundbulging friction weld seam 51 is removed by machining in a subsequentoperation. In this illustrative embodiment, the length of the stemconnection element 49 is selected in such a way that, when thelightweight valve 1 has been assembled, the connection region betweenstem connection element 49 and valve stem 3 is arranged outside thevalve cone hollow space. This design affords both the possibility offirst connecting the valve cone 5 to the valve disk 7 and the stemconnection element 49 and only then connecting the valve stem 3 to thevalve disk 7 and also the alternative method variant of connecting thevalve stem 3 to the stem connection element 49 in a first step and thenconnecting the valve cone 5 to the valve disk 7 and the stem connectionelement 49 in a second step.

The stem connection element 49 has in its region of connection to thevalve stem 3 the same outside diameter and the same shape as the valvestem 3, by virtue of which a continuous transition can be brought about.

Means for partial internal support of the thin-walled valve cone 5 areprovided on the stem connection element 49, which means are formed inthis illustrative embodiment by a thickening 53 formed on the stemconnection element 49 which—seen in the direction of the longitudinalcentral axis 2 of the lightweight valve 1—is located at an axialdistance from the bottom of the recess 23, or of that flat side of thevalve disk 7 facing the valve cone 5. The thickening 53 has a conicalsupporting surface 55 of all-round design in the illustrative embodimentaccording to FIG. 5, which is in bearing contact with an inner wallregion of the valve cone 5, by virtue of which the valve cone 5 issupported. The contour of the supporting surface 55 is designed tocomplement this valve cone inner wall region, by virtue of which contactover the entire surface can be ensured.

The distance of the thickening 53 from the valve disk 7 and its designare such that the valve cone 5 pushed onto the stem connection element49 is both centered in relation to the valve disk 7 and held at such adistance from the valve disk 7 that the valve cone 5 projects into therecess 23 with its end of greater diameter in the desired way.

The valve cone 5 differs from that described with reference to FIGS. 1and 2 in that it has a simpler shape which is more cost-effective toproduce, namely that of a disk spring.

It remains to state that the valve cone 5 is in each case supported andcentered by means of the thickening 53 at its end of smaller diameterand by means of the recess 23 at its end of greater diameter.

In the illustrative embodiment according to FIG. 5, it is to beemphasized as especially advantageous that the valve cone 5 has adiameter d at its end of smaller diameter which is markedly greater thanthe outside diameter of the valve stem 3, so that the valve cone 5 caneasily be slipped over the valve stem 3 even with the friction weld seam51 present. Owing to the disk form of the valve cone 5, the valve stem 3does not have to have a step either, that is a diameter jump, in orderto bring about a continuous transition between valve cone 5 and stemconnection element 49, as can be seen from FIG. 5. The valve cone 5bears flush against the thickening 53 in the transition region.

In an illustrative embodiment not shown in the figures, the thickening53 is formed on the valve stem 3. The connection location between valvestem 3 and stem connection element 49 is then located inside the valvecone hollow space. Alternatively, the stem connection element 49 can bedispensed with and the valve stem 3 having the thickening 53—as in theillustrative embodiment described with reference to FIG. 1—can bedirectly in contact and welded together with the valve disk 7.

In the illustrative embodiment according to FIG. 5, the stem connectionelement 49 has a blind hole opening 57 which extends in alignment withthe stem hollow space 39 and as far as the valve disk 7. In order for itto be possible to ensure uniform pressure conditions in the lightweightvalve 1, slit-shaped openings 57 arranged at 90° from one another, whichconnect the annular valve cone hollow space delimited by the valve cone,the valve disk and the stem connection element 49 to the blind holeopening 57, are provided in the stem connection element 49. Thelightweight valve 1 can be filled with a cooling medium which can spreadthroughout the lightweight valve 1 owing to the openings 59, whichcontributes to improved cooling of the valve.

The illustrative embodiment described with reference to FIG. 5 can befilled with the cooling medium especially easily by the valve stem, thevalve cone and the valve disk first being interconnected and the coolingmedium then being introduced via the open, free end of the hollow valvestem. The free valve stem end is then closed, for example by the stemendpiece being forged on.

Owing to its construction described above, the illustrative embodimentdescribed with reference to FIG. 5 is characterized by easymachinability of the seat/bearing surfaces (supporting surface 55 andrecess 23 or edge step 37) for the valve cone 5.

1-7. (canceled)
 8. A lightweight valve comprising: a valve stem; ahollow valve cone connected to the valve stem and having a greaterdiameter end region and an smaller diameter end region; and a valve diskclosing the valve cone and having a flat side facing the valve cone, thevalve disk and valve cone in a connection region having an at leastapproximately continuous transition, the valve disk being provided onthe flat side facing the valve cone with a recess, the recess defining acentering or supporting seat of the valve disk and the valve coneprojecting into the recess with the greater diameter end region ofgreater diameter, the valve cone being a separate component and fixed atthe smaller diameter end region to the valve stem or to a stemconnection element provided on the valve disk.
 9. The lightweight valveas claimed in claim 8 wherein the transition is conical.
 10. Thelightweight valve as claimed in claim 8 wherein the valve disk is ofdisk-shaped design and has a conical longitudinal portion in theconnection region, a cone angle of the conical longitudinal portionbeing the same as a cone angle of the greater diameter end region of thevalve cone.
 11. The lightweight valve as claimed in claim 8 wherein afurther centering or supporting seat for the end of smaller diameter ofthe valve cone is provided on the valve stem or the stem connectionelement.
 12. The lightweight valve as claimed in claim 8 wherein thevalve disk has a support for the valve cone.
 13. The lightweight valveas claimed in claim 11 wherein the valve is an internal combustionengine valve.